1. Field of the Invention
The present invention relates to a technology for establishing communication with another communication terminal.
2. Description of the Related Art
With the realization of miniaturization and lightweight of information terminals, it has become common nowadays for people to carry an information terminal. In association with this, study has been vigorously undertaken on the construction of wireless ad hoc network for on-demand communication. In an ad hoc network, base stations and access points are not necessary. It is therefore easy to build a network even in places where no such infrastructure exists. By using an ad hoc network, a plurality of users may enjoy a game together without being constrained in place, as they join each other, bringing their own portable game devices and communicating wirelessly.
An ad hoc network is built by allowing terminals to communicate with each other using technologies such as IEEE802.11 or Bluetooth. No problem with power is presented when a terminal is capable of receiving power supply from an external power supply. In the case of portable terminals, however, it is preferable that battery consumption be reduced as much as possible since such terminals are driven by limited battery power. To address this, a power-saving control process performed after establishing communication is standardized in communication standards such as IEEE802.11.
When two wireless communication terminals come within the communication range of each other, an ad hoc network is built by one of the apparatuses responding to a beacon signal from the other with a request to participate in a network. A communication terminal acknowledges the other communication terminal by performing scanning (search) and receiving a beacon signal transmitted therefrom. When scanning is performed continuously in a situation where it is uncertain whether the other communication terminal is within the communication range, significant power is consumed. A portable communication terminal is usually carried with a person. It is therefore expected that another communication terminal comes within the communication range as the person moves. For this reason, users have a desire to locate a partner for communication by pressing a button for execution of a search at intervals of 10-100 seconds. However, the operation for a search is inconvenient for users. It is desirable that the communication terminal be provided with the function for automatic search. Users also have a desire to let nearby terminals know the presence of their own terminals.